As a part of the ongoing BIPM key comparison BIPM.EM-K11.b, a comparison of the 10 V voltage reference standards of the BIPM and the National Metrology Laboratory (NML), Dublin, Ireland, was carried out from May to June 2008. Two BIPM Zener diode-based travelling standards (Fluke 732B), were transported by freight to NML.

At the BIPM, the traveling standards were calibrated with the Josephson Voltage Standard. Results of all measurements were corrected for the dependence of the output voltages on ambient temperature and pressure. The NML measurements were carried out by comparison with the mean of the NML voltage standard.

A least-squares method is used to reduce the data, which comprise the measured voltage differences and the predicted output EMFs of the reference devices.

The final result of the comparison is presented as the difference between the value assigned to a 10 V standard by the NML, at the NML, U_NML, and that assigned by the BIPM, at the BIPM, U_BIPM, which for the reference date is:

U_NML − U_BIPM = −0.56 µV; u_c = 1.32 µV on 2008/05/28,

where u_c is the standard uncertainty associated with the measured difference, including the uncertainty of the representation of the volt at the BIPM, the uncertainty of the representation of the volt at NML, and the uncertainty related to the comparison.

This satisfactory result shows that the voltage standards maintained by the KRISS and the BIPM were equivalent, within their stated expanded uncertainties, on the mean date of the comparison.

Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.

The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).